The present invention relates to an attachment structure for detachably attaching a workpiece holder to a movable body which is relatively movable with respect to a sewing needle.
A workpiece holder is used for holding a workpiece such as a fabric for embroidery stitching by a sewing machine, and conventionally, the holder is detachably held by a movable body. For example, a Japanese Utility Model Application Kokai(OPI) No. 62-122890 discloses an attachment structure for detachably attaching the workpiece holder. As shown in prior art FIG. 1 of the present application, a pair of guide pins 51a, 51b are implanted in a movable body 53 which is movable in synchronism with reciprocating motion of a sewing machine (not shown). The movable body 53 has a stepped portion where a pair of slots 53a, 53b are formed. Further a leaf spring 65 is fixed to the movable body 53.
A workpiece holder 59 for holding a fabric includes an inner frame 55 and an outer frame 57 to which one end portion of an attachment piece 63 is provided. The attachment piece 63 has an intermediate portion whose end face serves as engaging planes 61a, 61b engageable with the pair of guide pins 51a, 51b. Further, the attachment piece 63 has another end portion provided with pair of projections 63a, 63b.
For attaching the workpiece holder 59 to the movable body 53, the two projections 63a, 63b are inserted through the pair of slots 53a, 53b of the movable body 53 in a direction indicated by an arrow A, while the attachment piece 63 is slantingly oriented such that the vertical position of the projections 63a, 63b is lower than that of the holder 59. Therefore, the projections 63a, 63b are brought into engagement with the leaf spring 65 with the latter being resiliently deformed. Then, the attachment piece 63 is urged to be depressed downwardly. Accordingly, the engaging planes 61a, 61b are brought into engagement with the associating guide pins 51a, 51b. Thus, the attachment piece 63 is held by the movable body 53 through the leaf spring 65, to thereby fix the workpiece holder 59 to the movable body 53 in parallelism with a stitching plane.
Further, a Japanese Utility Model Application Kokai (OPI) No. 63-81890 also discloses an attachment structure. As shown in prior art FIG. 2 of the present application, a movable body 73 movable in synchronism with the reciprocating motion of a sewing needle is fixed with a pair of positioning pins 71a, 71b. A generally U-shaped leaf spring 75 is provided whose lower end portion is fixedly secured to a lower face of the movable body 73 and at a position below the positioning pin 71b. An upper end portion of the leaf spring 75 is formed with an elongated notch 75a and is directed toward the pin 71b, so that the pin 71b is positioned in an elongated notch 75a.
A workpiece holder 81 has an inner frame 77 and an outer frame 79 to which one end of an angled link arm 83 is fixedly secured. At one side end face of the link arm 83, a positioning notch 85 is formed which is engageable with the positioning pin 71a. Further, the angled link arm 83 is formed with a positioning hole 87 engageable with the positioning pin 71b. The leaf spring 75 is adapted for preventing the positioning pins 71a, 71b from being disengaged from the positioning notch 85 and the positioning hole 87, respectively.
For attaching the workpiece holder 81 to the movable body 73, the positioning notch 85 is brought into engagement with the positioning pin 71a as shown by two dotted chain line in FIG. 2, and the workpiece holder 81 is angularly rotated about the pin 71a in a counterclockwise direction in FIG. 2. During this angular motion, the link arm 83 is urgedly interposed, against the biasing force of the leaf spring 75, between the upper portion of the leaf spring 75 and an upper surface of the movable body 73. Next, the link arm 83 is lifted upwardly further against the biasing force of the leaf spring 75 in order to place the link arm 83 on the positioning pin 71b. At the same time, the link arm 83 is pressed toward the movable body 73 so as to provide engagement of the positioning pin 71b with the positioning hole 87. The engagements of the pins 71a, 71b with the notch 85 and the hole 87 can be maintained by virtue of the leaf spring 75. Thus, the workpiece holder 81 can be fixed to the movable body 73.
According to the conventional arrangement, as described in JP 62-122890 and as shown in prior art FIG. 1 of the present application, the workpiece holder 59 must be positioned between a sewing needle and a throat plate while preventing the holder 59 from abutting the sewing needle. Then, the two projections 63a, 63b must be engaged with the leaf spring 65 while avoiding mechanical interference between the engaging planes 61a, 61b and the guide pins 51a, 51b, and thereafter, the holder 59 is angularly rotated in the vertical direction for providing the engagement between the engaging planes and the guide pins, while still obviating mechanical interference between the sewing needle and the workpiece holder 59. Therefore, such angular movement may require skill and thus, the attachment and detachment work of the workpiece holder may be troublesome for an operator.
The same is true with respect to the other conventional arrangement described in JP 63-81890. This arrangement also requires angular rotational movement of the workpiece holder 81 within a limited narrow space defined between the sewing needle and the throat plate for the attachment and detachment work.